1. Field of the Invention
The present invention relates to an intake apparatus for supplying air to an engine, and more particularly, to an intake apparatus which is capable of suppressing noise.
2. Description of the Related Art
A schematic diagram of an intake apparatus is shown in FIG. 23. As shown in the drawing, an air cleaner 100 is comprised of an intake duct 101, a resonator 110, an air cleaner 103, an air cleaner hose 104, a throttle body 105, and an intake manifold 106. The intake air is sucked into the intake duct 101 through an inlet port 102, and is supplied to combustion chambers 109 of an engine through the resonator 110, the air cleaner 103, the air cleaner hose 104, the throttle body 105, and the intake manifold 106.
In the intake apparatus 100, noise which leaks from the inlet port 102 (this noise will be hereafter referred to as intake sound) becomes a problem. The intake sound has a relatively wide frequency range of 1 kHz or more. Further, a plurality of resonance peaks where sound pressure levels are extremely high are interspersed in this frequency range. Accordingly, the intake sound can be suppressed by making the resonance peaks small.
Accordingly, Unexamined Japanese Patent Publication No. 2002-21660 introduces an air cleaner having an air-permeable member. FIG. 24 shows a schematic diagram of the air cleaner disclosed in that publication. It should be noted that portions corresponding to those of FIG. 23 are denoted by the same reference numerals. As shown in the drawing, a portion of a dirty-side bottom wall 111 of the air cleaner 103 is formed by an air-permeable member 112. Of the plurality of resonance peaks, antinodes of standing waves which form the resonance peaks in a relatively low frequency range are located on the dirty side of the air cleaner 103. For this reason, according to the air cleaner 103 disclosed in the publication is capable of suppressing the sound in a relatively low frequency range in the intake sound.
However, according to the intake apparatus 103 disclosed in the publication, it is merely possible to suppress the sound in a relatively low frequency range. Namely, it is merely possible to suppress only part of the sound in a narrow frequency range.
In addition, if the air-permeable member 112 is disposed, noise which is transmitted through the air-permeable member 112 (this noise will be hereafter referred to as transmitted sound) is generated. The transmitted sound leaks to the interior of an engine compartment close to a vehicle compartment. For this reason, it is necessary to suppress the transmitted sound as well in the same way as the intake sound. Specifically, the sound pressure of the intake sound and the sound pressure of the transmitted sound need to be tuned over a wide frequency range. The tuning of the intake sound and the transmitted sound can be effected by adjusting such as the amount of air permeation of the air-permeable member 112.
However, according to the air cleaner 103 disclosed in the publication, a single air-permeable member 112 is merely disposed on the dirty side. For this reason, of the intake sound and the transmitted sound, it is only the sound in a relatively low frequency range that can be tuned. Namely, it is difficult to tune the sound pressure of the intake sound and the sound pressure of the transmitted sound over a wide frequency range.
Further, Unexamined Japanese Patent Publication No. Hei. 3-279664 introduces an intake apparatus having a resonator. FIG. 22 shows a schematic diagram of an air cleaner and its vicinities of the intake apparatus disclosed in the document. As shown in the drawing, an air cleaner 200 is comprised of a dirty-side casing 201, a clean-side casing 206, and an element 207. An intake duct 209 projects from an outer surface of a side wall of the dirty-side casing 201. A quarter tube member 203 communicating with the intake duct 209 is accommodated in the dirty-side casing 201. Portions of a bottom wall and a side wall of the dirty-side casing 201 are formed as a dual-use outer wall portion which also serves as an outer wall of the quarter tube member 203. A connecting tube portion 205 communicating with the interior of the quarter tube member 203 projects from the dual-use outer wall portion 104. A resonator 211 is connected to the connecting tube portion 205. An air cleaner hose 210 projects from an outer surface of a side wall of the clean-side casing 206. The element 207 partitions the air cleaner 200 into the dirty-side casing 201 and the clean-side casing 206.
The intake air flows in the order of the intake duct 209, the quarter tube member 203, the resonator 211, the quarter tube member 203 again, the dirty-side casing 201, the element 207, the clean-side casing 206, and the air cleaner hose 210. The intake air is then supplied to combustion chambers (not shown) of the engine through a throttle body (not shown) and an intake manifold (not shown). Meanwhile, the intake sound is suppressed by the resonator 211.
However, according to the intake apparatus disclosed in that document, a space for disposing the resonator 211 is required. For this reason, the space for mounting other members in the engine compartment is made narrow.
In addition, the resonator 211 is merely capable of suppressing only the sound in relatively medium and high frequency ranges. Namely, the resonator 211 is difficult to suppress the intake sound over a wide frequency range.